1. Technical Field
This disclosure relates to identification of blind landmarks on orthopaedic implants.
2. Description of the Related Art
The interlocking nail has significantly widened the scope for intramedullary (IM) fixation of long bone fractures. Anchoring an IM nail to a bone makes the construct more stable longitudinally and stops rotation of the nail within the bone. A typical IM nail fixation surgery involves a combination of jigs, x-ray imaging, and manual “eye-balling” to locate and drill the distal screw holes and to install the screws in the screw holes.
In IM nail fixation surgery, an IM nail is inserted into the canal of a fractured long bone in order to fixate the fractured ends together. Typically, the proximal locking is performed first and is usually carried out with a jig. Nail deformation during intramedullary insertion, however, may make a jig inaccurate for the distal screws. In fact, the positioning of the distal locking screws and alignment of the drill for the drilling of the distal screw holes is the most time consuming and challenging step of the implantation procedure. The two main reasons for failure in distal locking are (1) incorrect entry point on the bone and (2) wrong orientation of the drill. If either of these problems occurs, then the drill will not go through the nail hole. An inaccurate entry point also compounds the problem as the rounded end of the drill bit often slips, damaging healthy bone rendering it difficult to place another drill hole next to the inaccurate hole. Inaccurate distal locking may lead to premature failure with breakage of the nail through the nail hole, breakage of the screw, or the breaking of the drill bit within the bone.
Manual techniques are the most common and accepted techniques for sighting the distal screw holes. The majority of manual distal targeting techniques employ a guide bushing or cylindrical sleeve that guides the drill. The mechanisms of aligning the guide bushing and keeping it in place differ. There are cases where the surgeons use a guide bushing cut in half longitudinally or a full guide bushing to help steady the drill bit. In either situation, the surgeon will incise the patient and insert the drill through the incision. Manual techniques are based primarily on the surgeon's manual skill and make use of radiographic x-ray imaging and mechanical jigs.
Another method for achieving this on long nails is by using a technique called “perfect circles” with the aid of a C-shaped arm. This is where the patient and the C-arm are oriented such that when viewing the implant fluoroscopically the hole through which the screw is to pass appears to be in the shape of a circle. If the C-arm is not perpendicular to the hole then the hole appears oblong or even absent.
A need exists for an improved system and method for accurately and dependably targeting landmarks of a medical implant. Further, a need exists for accurately positioning the distal locking screws and aligning the drill for the drilling of the distal screw holes. Still further, a need exists for an improved system for targeting landmarks whereby the components may be easily sterilized or autoclaved and reused again.